Yes! I just downloaded K9 yesterday because I was so tired of it, started happening maybe 3 weeks ago. It seems to still sync with my primary account, but none of my secondary like my work e-mail. So I'll open it up and have like 10 email waiting for me that I really needed to have seen right away. Very annoying. K9 has been working great so far...

Ive noticed that i dont get emails recently. That is, until i manually go into gmail and refresh the inbox. sometimes when my phones idle for a while the data cuts off, but i dont have the data saver thing on. How can i fix my gmail and stop the data from cutting off?

If you go into settings->accounts, tap on your GMail account, is the GMail sync checkbox turned on? (If it is disabled, then I think that data sync is turned off completely. Try putting the power control widget on a home screen, look for the icon that is second from the right - it looks like a circle containing two arrows pointing to each other - and, if that control is turned off, turn it back on again.)